The present invention relates to a valve with high flow resolution within a flow range, which valve comprises a valve housing and a valve plug with a flow regulating slit.
For setting the temperature in a driver's space or passenger space in a vehicle it is possible to use, for example, a rotary valve regulating the flow of hot water through a heat exchanger. The valve may be set either manually or automatically.
In a known valve comprising a valve plug with a flow regulating slit, the valve plug's inlet is arranged centrally relative to the valve plug's outlet and they are connected to one another via a channel which passes through the center of the valve plug, whereby the flow path when the valve is fully open is along a straight line through the valve plug. Turning the valve plug through approximately 90-100 degrees closes the valve. Further turning reopens the valve. In such cases turning the valve from fully open to fully closed position involves a travel distance of about 90-100 degrees. The flow regulating slit is arranged at the portion of the travel distance which does not comprise the inlet to the cavity through the valve plug, i.e. usually along approximately 30 degrees of the valve plug's periphery.
To enable the valve to be fully closed there needs to be on the shell surface of the valve plug a vacant area at least as large as the valve plug's inlet. A case where the inlet extends across 30 degrees of the shell surface will thus require 30 degrees of the shell surface in order to achieve a fully closed valve, thus leaving approximately 30 remaining degrees of the shell surface to cater for manufacturing tolerances. This makes it difficult in practice to arrange a flow regulating slit which extends across more than 45 degrees of the shell surface.
A problem with previously known valves is that their flow resolution, i.e. the change in flow per angle unit of rotation of the valve plug, is relatively low, which makes it difficult to set the right flow of hot cooling water from the vehicle's engine through the heat exchanger, which flow determines the temperature of the air flowing out from the heat exchanger. It is at low hot water flow through the heat exchanger that it is desirable to increase the region of high flow resolution. In the case of automatically operated valves, the difficulty in setting the right temperature results in the valve moving violently to and for, which may lead to premature failure of the valve. In the case of manually set table valves, the driver has to turn the valve plug to and for with great precision in order to achieve the desired temperature.